Television scanning system



2 Sheets-Sheet 1 Filed Aug. 9, 1930 flamzdzzmze Aug. 7, 1934. H. P. boNLE 1,969,456

TELEVISION SCANNING SYSTEM I Filed Aug. 9, 1930 2 Sheets-Sheet 2 Patented Aug. 7, 1934 'UNITEID'J STATES 1,969,456 TELEVISION SCANNING SYSTEM Harold P. Donle, Meridcn, Conn assignor to Radio Inventions, Inc.,' a corporation of New York ApplicationAugust 9, 1930, Serial No. 474,088

12 Claims. (Cl.178'-6) This invention relates to television scanning systems and especially to devices of a moving character. for the analysis of optical images and their conversion into electrical Signals, or for 5 the reconstruction of optical images from the signals correspondent to the analysis made at the transmitter.

These moving scanning devices are usually large in size, or if constructed smaller than several feet in diameter, are subject to certain errors of operation, which may cause both analysis and synthesis of the images to be attended with distortion.

My invention purposes to greatly reduce the size of such apparatus and at the same time to overcome errors arising from such a small construction. As an example, an apparatus constructed according to my invention, with an overall dimension approximately 24 x 27 x 30 cm. will give results substantially equivalent in quality to those theoretically obtainable from a scanner of the usual type, employing a disc with a diameter of 75 cm. Actually, due to further advantages which will be set forth in detail. in the following disclosure, better quality may be expected from scanning apparatus constructed according to my invention. Such an apparatus will give a picture approximately 37 x 50 mm.

One principle of my invention can be illustrated by consideration of a scanning device employing a radially slitted disc and a drum slitted longitudinally on its periphery, both of relatively small size, and having their position and movement so designed and disposed as to scan an optical image by the co-a-ction of their relative sets of slits. The combination with these elements of an optical system operating upon the distorted image produced, so as to correct the distortion of the same, gives one device illustrative of my invention.

Fig. 1 is a front elevation of a scanning mechanism constructed according to my invention.

Fig. 2 is a side elevation of the mechanism of Fig. 1.

Fig. 3 illustrates someof the optical principles involved in my corrector mechanism, by a simplified detail of the whole device.

Fig. 3a is a side elevation of Fig. 3.

Fig. 4 shows another form of construction for a scanner embodying my invention, where two discs are employed, instead of a drum and. a disc.

Fig. 4a is a side elevation of the mechanism of Fig. 4, viewed from the right side.

Referring to Figs. 1 and 2 of the drawings, 1 is a small disc which, owing to its small diameter may be made very thin and light in weight, for example, of materials of low specific gravity such as bakelite. This disc carries at its periphery twelve slits such as slit 2. Drum 3 has upon its peripheral surface ten slits 4. -These slits are wider than those in the disc, since theyare not magnified optically, andare moved by the rotartion of the drum, sothat they pass vertically behind the lens 5. A Suitable size for the drum slits is 1.5 mm.. and for the disc slits- 0.75 mm. Plano convex lens 5 is of the type known as cylindrical and is mounted in a supporting frame 6. Supporting framework '7, carriesa motor ,8, whose shaft has at one end, a coupling ,device 9, fastening the disc to the same, and at theother end a worm 11,.driving a gear 12 at a 40 to 1 ratio. This worm causes drum 3 -to rotate at a much slower speed than the disc. Gears 12, 13, 14 trans,- mit the driving motion to the drum. The shaft 15, carrying the drum 3, is provided with a collar 16, having a flange 18 adjacent to, gear 14, which collar also is firmly affixed to and rotateswith the shaft 15; The final gear 14 of the drive has a collar 1.? on one side androtates freely uponlshaft 15. A Spiral spring 19 surrounds shaft 15.; This spring is compressed at will by movinglthehollow spring seat cap 20 along the shaft, upon' which it turns freely, towards the collar 1'7. A ball-bear ing 21 transmits to this cap 20 the longitudinal motion of rod 22, movable within-fixed sleeve by the angular rotation of clutch control lever 23, fastened to rod 22 and moving within a slot'cut spirally in the sleeve 25, in such fashion" that the angular motion of lever 23 causes the rod to move longitudinally, thus pushing cap 20 along shaft 15 and compressing spring 19, which causes collar 17 and attached gear 14 to be pressed more firmly against fiange 18 of collar 16, whereupon the friction of the adjacent surfaces of the gear and the collar cause them to rotate simul-. taneously. This mechanism is thus Seen to con-- stitute a clutch device whereby the drive or release of drum 3 can be volitionally determined by the operation of the controlling'lever 23.- The necessary supports, bearings, shafts, and'other mechanical essentials for the co-operation ofthe drive andclutch mechanisms are sufficiently indicated in the drawings.

A synchronizing regulator is shown incorporated at one end of the motor shaft, where coils are shown in cross section as wound about the pole pieces 31 of the cores 32 fastened by screws 34 so as to remain stationary- Armature 35 is carried by the motor shaft, and upon application of, for example, a cycle synchronizing current to the coils 30, this armature is subject to-the magnetic field of the coils and tends to exercise upon the shaft 10, to which it is firmly attached;

a force, of either an accelerative or a decelerative I nature, according to the relationship of the actual speed to the synchronous speed, such as' to aid in maintaining the shaft and disc speed at 3600 R. P. M., for example. 1

A Spherical piano-convex lens 40, mounted within a supporting frame 41, is mounted im'-' mediately before the cylindrical lens 5, and has its distance therefrom adjustable by means of the thumb screw45 which determines the point of fastening of its supporting frame in the slotted support member 42. A mirror 43 on a support 44 is set at an angle of approximately 45 withinthe rotating drum, in such fashion as to change the direction of the path of the light rays transmitted through the drum and impinging upon it, through an angle of approximately 90, in accordance with well known optical principles, thus delivering the image to the exterior of the apparatus through the open end of the cylinder 3. It is preferred that this mirror be constructed in such manner as to avoid multiple reflexion, as for instance, by making it of bare metal, instead of the more usual glass covered metal.

In order better to illustrate the action of this device, a lightproducing device, responsive to the received electrical signals, is indicated schematically at 50, where is shown a typical glow lamp with plate electrodes.

Referring now to Fig. 3, some of the principles of my optical correction device are illustrated by the showing of a disc and cylindrical lens only. I In the simple form here shown, f-g is a line making an angle with the vertical optical axis of the system, which latter is parallel with the ends of the cylindrical lens 5. This line f--g represents one of the slits of scanning disc 1, as it is entering the active scanning field from the left side. As the slit reaches the centre of the field it will manifestly be parallel to the vertical axis thereof, and as it passes towards the other side, its angle of inclination will be reversed. Now cylindrical lens 5, by virtue of the optical properties of such lenses, will tend to cause the line ,f-g to assume the apparent position of the line h-i. Thiscorrective action will likewise be exerted upon any other line not perpendicular to the horizontal axis of the lens such as slit y'-Ic leaving at the right, which will tend to appear as line Z-m, and the degree of correction will be automatically determined by the degree of inclination which the line suffers, with respect to the vertical h-z. This causes the slit which is passing across the field and making the continuously changing angle with the horizontal, as described in the first part of this paragraph, to be subject to this correcting action, in exact proportion to its degree of angular departure from the 90 angle desired. The result is that a line passingacross the field, instead of producing a wedge-shaped picture due to the physical tilting of the slits in the disc will appear to produce the desired rectangular shaped picture. This optical correction of the apparent field occurs because of the phenomenon already described. 7

Fig. 3a shows-in side elevation the disc and cylindrical lens of Fig. .3, illustrating their placings relative to one another. It is to be under stood that in this figure, as also in Fig. 3, the spherical lens of Figs. 1 and 2 is omitted for the sake 'of greater clarity in explaining theprinciples involved in the use of the cylindrical lens, and that my'invention is in no way dependent upon the presence or" this spherical lens, which is merely used for ancillary purposes, as described in 1 connection with Figs. 1 and 2.

' speed commensurate withthe disc of Figs. .1 and 2, while worm gears 51 and 52, reduce the speed of disc B to one commensurate with that'oi the drum 3; of Figs. 1 and 2. This reduced speed is transmitted byshait 54 and pinion gears 53 and 55 to cause the disc B to rotate slowly in com-- parison with disc A. A cylindrical lens 56 corrects the distortion due to the angle of the slits in the disc A, by the principles explained in connection with Fig. #3. -In this case it is evident that the angular position of the slits in disc B will also cause an error. This error may be partially or completely compensated for by placing the cylindrical lens not parallel to the surface of the discs, but at an angle thereto. This angular displacement of the lens will tend to correct the error due to the angular'position of the slits in the disc B. A special lens withinore than one axis of curvature may be constructed according to well-known optical laws, which lens will accomplish both corrections simultaneously.

Fig. 4a shows in side elevation the variant form of Fig. 4, as seen looking from the right side of Fig. 4. The relative distances of the parts is ap-- proximately indicated in this figure, where the discs are about 20 cm. in diameter, and the angle of inclination of lens 56 with respect to the discs is indicated.

In all the foregoing descriptions, it isunderstood that the usual mechanical expedients and optical housings and shieldings are employed, as well aszsuch framing apertures and such projection devices as are necessary or desirable and familiar in the art. The dimensions and numerical values which have been given are understood .to be merely illustrative, and subject to variation in accordance with well understood optico-electrical principles, as employed in the television art.

In considering the action of the device of Figs. 1 and 2, as a receiver, it will be seen that the light output of the electro-optical responsive device 50 is scanned horizontally by the slits in the disc 1, which makes 4 revolutions per picture. Since the disc has 12 slits, this means that 48 horizontal lines have been scanned, while the drum has scanned once vertically, thus giving 48 line scanning. The light beams delivered by the disc are magnified in area by lens 40, optically corrected, as hereinbeiore explained, by the lens 5, and delivered to the vertically moving slits of drum 3. With the gear ratio and number of slits here illustrated, it will be seen that during 4 revolutions of the disc, the drum will have moved revolution, so that a single slit of latter will have vertically scanned one complete picture. The now completely synthesized image is reflected by the mirror 43, to the observer or to any screening, framing, projection, or viewing devices that may be desired.

As a means of securing synchronization, currents of proper frequency are supplied to the coils 30 causing armature 9 to be acted upon magnetically. These currents may be secured from a source of power identical in frequency with that driving the transmitter, or may be derived from certain signals transmitted over a channel common to both these signals and the television signals, by means such as those disclosed in, my copending patent application Ser. #322,360, or otherwise, or from signals transmitted over. another channel, or otherwise secured.

I The securing of the proper phase relationship of the receiving scanner tothe signals being received, is readily accomplished, without interruption oi reception, and without substantially ITO til

disturbing the speed of the operating motor. .This is done by the use of the clutch device shown,

whereby the slow moving scanning membercan be disconnected momentarily from the drive device, so that it will lose speed during this period of disconnection..

An alternative method is to cause the clutch device to slip by applying a retarding or braking force to the driven member thereof, thru mechanical motion of the frame can be used, as

disclosed in my co-pending application Ser. #425,785. In order to secure framing in the horizontal direction it is necessary that the rapidly moving disc be in the proper phase relationship to the signals. This relationship can be altered while in operation by changing the amount of electrical energy supplied motor 8, so that its armature will tend to angularly lead or lag with respect to the synchronous speed fixed by regulator 32, 35,

or by rotating {the synchronizing pole pieces 31 It is of assistance in secur- -t is possible to use synchronizing methods which inter-relate the angular positions of the corresponding scanning members at :the transmitter and the receiver, in such fashion as to automatically bring about this framing. In all cases Where the synchronizing action at'the receiver is directly or indirectly upon the shaft to which the scanning disc is afiixed, it is important that the disc have its slits in proper angular relationship with the shaft. This adjustment, of course, can be made while stationary, or while in operation by such mechanical means as disclosed in my co-pending application Ser. #425,785. This last mentioned means can likewise be employed to change the angular displacement of the scanning drum, instead of the clutch'herein shown.

The advantages arising from the employment of my invention are both electrical and mechanical in nature and some of them are here mentioned. By the employment of scanning mechanism in accordance with my invention, the size of the apparatus necessary may be keptmore nearly commensurate with that of the usual apparatus employed for purposes of voice reception. The reduction in the size of the moving members, allows them to be much lighter in weight, of less inertia, and therefore much more amenable to rapid changes of speed, as may be reqvired for purposes of securing or maintaining synchrony. The difficulties due to the tendencies of large rapidly moving members to set up vibrations, are avoided in my invention. The small size of my moving members, especially of the disc, allows their construction of thin materials of low specific gravity, such as bakelite, fibre, thin metal, or the like. This reduces the difiiculty with over-run- .entirely-in one member, while I cause the pro.-

ning or hunting. while adjusting to secure synchronism.

By theuse of small thin moving members, as made possible by my-invention, it is easier to produce accurately sized and positioned aper-"SG tunes for scanning purposes, than in the case of duction of a virtual optical aperture by the coaction' of two actual physical slit-like apertures. These slits of my invention are much less apt to fill with dirt than the small physical apertures of the commonly used forms of disc apertures. '95 All this promotes greater accuracy of scanning.

By my separation, in a physical sense,1of the horizontal and vertical scanning, I am the more easily enabled to modify the-degree of elementary subdivision in each of these dimensions, or their respective relationships to one another, or to the general rate of scanning, number of im ages per unit time, etc.

' By such changes as indicated, I can scan with greater detail in ahorizontalthan' in a vertical sense, which is desirable in certain casesas disclosed in my co-pending application Ser.

#433,670. Another advantage of my invention is that the framing of the received image can be readilyaccomplished by the various means mentioned, while the apparatus is in =motion. This not only, prevents interruption of reception, but allows the operator to see instantly the effects of the adjustments which he is making, which is of the greatest importance in facilitating the adjustments.

A further advantage of mydevice is the small amount of power required to drive the same, in comparison with the usual scanning mechanisms, which include discs of large diameter and heavy mass. The amount of power required to rotate the disc increases very rapidly as the diameter of the disc increases. This increase-is far more than the ratio of the relative diameters of a small and -,a large disc would indicate. My device requires to drive it only a fractionof the, power usedv to rotate the usual sized scanning discsr Another advantage of the small disc is that the slits may be made nearer the periphery, than in the case of the large discs, and therefore farther apart than permissible without my optical corrective device. 7 j

By suitable changes this form of scanning apparatus can be used as a transmitting'scannerh The substitution of a photo-electric cell for the reproducing lamp shown in the drawings will allow this result. Other arrangements of light sources and light sensitive cells, such as are well 140 known in the art, can easily be employed for transmission with the use of my invention.

Bysuitable re-arrangements of parts the path of the light thru the scanning apparatus can be reversed, so that the drum motion will cause-a 115 series of light beams to move across the field in a parallel disposition, and the .disc will scan these beams in a perpendicular direction.

My invention can be varied in its details with:

out departing from the spirit thereof, which embraces broadly the employment in scanning received apparatus of small sized moving members, and the optical correction of the distortion arising from the use of such small members.

I claim:

1. A television scanning system including a disc-like rotating member, with radial slits therein, scanning an optical image in one dimension, a drum-like member rotating at a speed related to the speed of the disc member and having longitudinal slits therein, scanning the optical image in the other dimension, and an optical correction system co-operating with these two separately moved sets of slits so that they are virtually maintained substantially at right angles to one another in respect to their optical action.

2. In a television apparatus, a rotary drum with a plurality of slits, a disc with a plurality of slitsand-rotating in a plane substantially parallel to a plane tangent at the surface of the drum, and an optical correction system for causing lines inclined with respect to one another to become substantially parallel in their optical effeet, the drum and disc co-operating to optically scan an image, and the optical correction system co-operating to rectify the initial obliquity of the scanned image caused by the oblique character of the slits in the disc.

3. An optical correction apparatus for television scanning systems including at least one scanning member, having radially disposed slits and a stationary substantially cylindrical lens axially at right angles to said slits operating to give a virtually parallel optical disposition to the radially disposed slits.

4. In television scanning, the method of optically correcting for obliquity of aperture definition' in two dimensions, by a single stationary substantially cylindrical lens, which includes correcting in one scanning dimension by the optical action of the refractive properties of said lens, and correcting in another dimension by the obliquity of the position of said lens relative to the aperture to be corrected in that dimension.

5. A device for television scanning purposes embracing a plurality of moving members having non-parallel slits, means for moving them so that the optical aperture caused by their intersection sweeps over an'image, and an optical device maintaining the virtual optical relationship of the co-acting slits at all times substantially rectangular, said optical device including a stationary cylindrical lens having an axis substantially at right angles to said non-parallel slits.

6. A television receiver having an electrical optical translating device and a viewing device and means for causing the optical interaction of said two devices, including a drum having a circumferentially disposed set of slits, a disc having a radially disposed set of slits, and a cylindrical lens, said sets of slits being so positioned and moved with respect to one another and to the incoming, television signals as to reconstruct the optical image correspondent to the electrical signals, said cylindrical lens. being so constructed and positioned with respect to the sets of slits as to rectify the obliquity in one dimension of the optical image, due to the radial disposition of said slits in the disc, and said Viewing device being so constructed and disposed as to deliver the rectified image resultant fromthe interaction of the electric optical translating device, the sets of slits, and the cylindrical lens, to a point suitable for proper visibility of the. same.

I. A television transmitter. having a light source device and ailight sensitive device, and means for causing the optical interaction of the said two devices including a drum with parallel slits on its surface, a disc with radial slits therein, the drum and disc cooperating to optically analyze the image to be transmitted, said means also including a cylindrical lens cooperating with the radial slits of the disc so as to cause their effective optical action to be as though they were parallel and untainted'by any. obliquity,

8. A television scanner including a radially slitted scanning member, means for moving said member so as to scan in one direction, a second slitted scanning member, means for moving said second scanning member so that its slits optically intersect the slits of said first scanning member and a stationary cylindrical lens so placed with regard to the optical intersection of said two sets of slits that it corrects for the radial arrangement of said first set of slits and gives a substantially rectangular form to the scanned image.

9. In television apparatus, a rotating drum shaped member provided with longitudinal slits, a rotating disc shaped member provided with radial slits and optically co-active with the drum member, coupling devices for varying a normally fixed relationship between their respective rotations, means for causing their rotation, and optical corrective means, said rotary means scanning an optical image by the constructive aperture due to their coaction, and said optical corrective means maintaining said constructive aperture optically substantially rectangular.

10. Television scanning apparatus including a Y,

luminous image to be scanned, a disc having slits rotated before said image, a substantially spherical lens magnifying the path of the light passing through the slits of the disc, a substantially cylindrical lens, tending to correct any non-alignment of the light path due to non-parallelism of the slits in the disc, a substantially cylindrical drum with an open end having slits rotated before the cylindrical lens, a mirror element located substantially within the drum and reflecting through the open end of the drum the light passing through the slits in the drum and impinging upon the surface of said mirror, said slitted disc and slitted drum being moved at speeds appropriate to the scanning of said luminous image.

11. Television scanning means comprising a source of modulated light, synthesizing means operating in two dimensions to distribute the optical output of said source over a planar area. said means causing illumination of said area in a planar configuration having non-parallel sides, and a stationary symmetrical cylindrical optical corrective device by means of which said planar configuration may be viewed by an observer, said device being arranged so that by its optical characteristics it produces a modified image of said planar configuration magnified in only one dimension.

12. Television apparatus comprising scanning means which form a distorted image, and a stationary symmetrical cylindrical optical corrective device by means of which said image may be viewed by an observer, said device being arranged a HAROLD P. DONLEK 

